/*
 * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.metrics;

import java.util.Collections;
import java.util.Iterator;
import java.util.function.Supplier;

/**
 * Default "no op" {@code ApplicationStartup} implementation.
 *
 * <p>This variant is designed for minimal overhead and does not record events.
 *
 * @author Brian Clozel
 */
class DefaultApplicationStartup implements ApplicationStartup {

    @Override
    public DefaultStartupStep start(String name) {
        return new DefaultStartupStep();
    }


    static class DefaultStartupStep implements StartupStep {

        boolean recorded = false;

        private final DefaultTags TAGS = new DefaultTags();

        @Override
        public String getName() {
            return "default";
        }

        @Override
        public long getId() {
            return 0L;
        }

        @Override
        public Long getParentId() {
            return null;
        }

        @Override
        public Tags getTags() {
            return this.TAGS;
        }

        @Override
        public StartupStep tag(String key, String value) {
            if (this.recorded) {
                throw new IllegalArgumentException();
            }
            return this;
        }

        @Override
        public StartupStep tag(String key, Supplier<String> value) {
            if (this.recorded) {
                throw new IllegalArgumentException();
            }
            return this;
        }

        @Override
        public void end() {
            this.recorded = true;
        }


        static class DefaultTags implements Tags {

            @Override
            public Iterator<Tag> iterator() {
                return Collections.emptyIterator();
            }
        }
    }

}
